1. Field of the Invention
The present invention relates generally to an electronic component having an electronic circuit device sealed therein and a method of manufacturing the same, and, more particularly, to an electronic component to be mounted on a circuit board and having a surface acoustic wave device or a semiconductor integrated circuit device sealed therein, as well as to a method of manufacturing the same.
2. Description of the Related Arts
Electronic appliances use a multiplicity of electronic components in each of which is hermetically sealed an electronic circuit device such as a semiconductor integrated circuit device or a surface acoustic wave (hereinafter, referred to as SAW) device. Such a multiplicity of electronic components are mounted on a single circuit board. Recent electronic appliances have a tendency toward miniaturization and low prices. This necessitates miniaturized and low-priced electronic components for use therein. Prevailing electronic components often employ a typical structure in which the electronic circuit device is sealed in a ceramic or metal package. However, in order to achieve further miniaturization and low prices there have been proposed electronic components making use of substrates themselves formed with electronic circuit devices for sealing of the electronic circuit devices.
Referring to FIGS. 20A and 20B, an electronic component is shown having a structure that is disclosed in xe2x80x9cOptimizing AQP SAW Resonators for Reduced Vibration Sensitivityxe2x80x9d published in IEEE Ultrasonic Symposium, 1995. FIG. 20A is a side elevation of an electronic component 110; and FIG. 20B is a sectional view of the same taken along a line Axe2x80x94A of FIG. 20A. The electronic component 110 is an SAW resonator. The SAW resonator includes comb-shaped electrodes 116, 118, 120 and 122 that are formed on a main surface 114 of an SAW substrate 112. A glass sealing wall 126 is formed on a quartz substrate 124 and is fused to the main surface 114 of the SAW substrate 112. The sealing wall 126 is formed so as to enclose an SAW device formed on the SAW substrate 112. The SAW device is hermetically sealed by the SAW substrate 112, quartz substrate 124 and sealing wall 126. The comb-shaped electrodes 116, 118, 120 and 122 extend beyond the sealing wall 126 so that their extremities, i.e., electrodes pads 128, 130, 132 and 134 are connected via bonding wires not shown to a circuit board not shown. In the step of assembling such two substrates into the electronic component 110, the assembly is typically carried out for each electronic component.
When fabricating the electronic component 110 depicted in FIGS. 20A and 20B, the sealing wall 126 may be heated upon fusing of the sealing wall 126 made of glass, polyimide resin or epoxy resin onto the main surface 114 of the SAW substrate 112, with the result that gas may be generated at the sealing wall fused portion. The thus generated gas may possibly attach to the SAW device electrodes inside the sealing wall, resulting in degradation of the SAW device characteristics.
The present invention was conceived in order to overcome the above problems. It is therefore the object of the present invention to provide an electronic component having a structure capable of effective removal of gas that may be generated upon the fusion of sealing walls.
According to a first aspect of the present invention there is provided an electronic component to be mounted a circuit board comprising a first substrate having an electronic circuit device and an electrode pad on one main surface of the first substrate in electric connection with the electronic circuit device; a sealing wall whose one face is closely adhered to the one main surface of the first substrate, the sealing wall being configured to enclose the electronic circuit device with the electrode pad arranged outside of the sealing wall; a second substrate closely adhered to the other face of the sealing wall; an opening formed in the second substrate at a site confronting the electrode pad; and an electrically conductive member extending through the interior of the opening for electrical connection with the electrode pad.
In the electronic component of the present invention, the electrically conductive member may comprise a bump disposed on the electrode pad.
In the electronic component of the present invention, the electrically conductive member may comprise a first bump disposed on the electrode pad for electrical connection with the electrode pad; and a second bump disposed on top of the first bump for electrical and physical connection with the circuit board.
In the electronic component of the present invention, the electrically conductive member may comprise a first bump disposed on the electrode pad for electrical connection with the electrode pad; and a second bump disposed on top of the first bump for electrical and physical connection with the circuit board; the first bump being a gold bump, the second bump being a solder bump.
In the electronic component of the present invention, the second substrate may have a second sealing wall around the opening configured to enclose the electrically conductive member.
In the electronic component of the present invention, the electrically conductive member may comprise a first electrically conductive member disposed on an inner wall of the opening for being electrically and physically connectable to the circuit board; and a second electrically conductive member disposed on the electrode pad for being electrically connected with the first electrically conductive member and with the electrode pad.
In the electronic component of the present invention, the electrically conductive member may comprise a first electrically conductive member disposed on an inner wall of the opening for being electrically and physically connectable to the circuit board; and a second electrically conductive member disposed on the electrode pad for being electrically connected to the first electrically conductive member and to the electrode pad. The second substrate may be a multi-layer substrate carrying one or more circuit elements thereon. In this case, the circuit element can be an element such as an inductor, a capacitor or a resistor having certain electrical characteristics and capable of being connected to other elements to form a circuit. The multi-layer substrate can be, for example, one having a structure in which a plurality of insulating layers and electrically conducting layers are disposed one on top of the other.
In the electronic component of the present invention, the sealing wall may be made of an insulating material, the material having an adhesion to at least one of the first substrate and the second substrate. The sealing wall may be made of a material selected from a group consisting of glass, polyimide resin and epoxy resin.
In the electronic component of the present invention, the electronic circuit device may be a surface acoustic wave device.
In the electronic component of the present invention, the first and second substrates may be made of the same material.
According to a second aspect of the present invention there is provided a method of manufacturing an electronic component, the electronic component to be mounted on a circuit board comprising a first substrate having on its one main surface an electronic circuit device and an electrode pad in electric connection with the electronic circuit device; a sealing wall whose one face is closely adhered to the one main surface of the first substrate, the sealing wall being configured to enclose the electronic circuit device with the electrode pad arranged outside of the sealing wall; a second substrate closely adhered to the other face of the sealing wall; an opening formed in the second substrate at a site confronting the electrode pad; and an electrically conductive member extending through the interior of the opening for allowing the electrode pad and the circuit substrate to be electrically connectable to each other; the method comprising a first step in which one face of each of a plurality of sealing walls is closely adhered to one main surface of the first substrate which has on the one main surface a plurality of electronic circuit devices formed in a plurality of circuit regions and a plurality of electrode pads in electric connection with the plurality of electronic circuit devices, the plurality of sealing walls each configured to enclose each of the plurality of electronic circuit devices with each of the plurality of electrode pads arranged outside of each of the plurality of sealing walls, and in which the second substrate is closely adhered to the other faces of the plurality of sealing walls, the second substrate having a plurality of openings at sites confronting the plurality of electrode pads; a second step in which an electrically conductive member is formed on each of the plurality of electrode pads, the electrically conductive member being in electric connection with each of the plurality of electrode pads; and a third step in which the first substrate, together with the second substrate, is severed for each of the plurality of circuit regions, to obtain a plurality of electronic components.
In the electronic component manufacturing method of the present invention, the first step may include a step in which the plurality of sealing walls are closely adhered to the first substrate after formation of the plurality of sealing walls on the second substrate, or alternatively it may include a step in which the plurality of sealing walls are closely adhered to the second substrate after formation of the plurality of sealing walls on the first substrate.
In the electronic component manufacture method of the present invention, the second step may include a step in which the electrically conductive member is formed on each of the plurality of electrode pads through a corresponding one of the plurality of openings.
In the electronic component manufacture method of the present invention, the electrically conductive member may comprise a bump.
In the electronic component manufacture method of the present invention, the electrically conductive member may comprise a first bump disposed on each of the plurality of electrode pads for electrical connection with the each of the plurality of electrode pads; and a second bump disposed on top of the first bump for electrical and physical connection with the circuit board. The second step may include a step in which the first bump is formed on each of the plurality of electrode pads through a corresponding one of the plurality of openings, after which the second bump is formed on top of the first bump.
In the electronic component manufacture method of the present invention, the first electrically conductive member may previously be formed on an inner wall of each of the plurality of openings, the first electrically conductive member being electrically connectable to the circuit board, and the second step may include a step in which a second electrically conductive member is formed on each of the plurality of electrode pads, the second electrically conductive member electrically connecting the first electrically conductive member and each of the plurality of electrode pads.
In the electronic component manufacture method of the present invention, the second step may be carried out posterior to the first step.